Question

I’m have beginner skills and am hoping someone can help me with a complex script in JavaScript ECMA-262 (as basic a JS script as possible, since the program I am using has only older implementation of ECMA-262. So some some array functions like “splice” even “concat” are not found in the language reference for this program. But basic JS works OK).

I am trying to create an array totaling 6 numbers from 2 separate subarrays (subarrayA=1,2,3 and subarrayB=4,5,6), alternately placing a number (chosen randomly from each subarray) from each subarray into the final 6 item array. Also, no duplicates.

So, for example, 3,6,1,4,2,5.

I’ve tried online searching, this board, trying out zipper methods from 2 subarrays, % to pick out odd/even, etc. So far, nothing has worked. But at least I’ve gotten some more knowledge allowing me to ask the question in a way that may help create a more specific solution. I would hard code this, but I think that the number of possible variations/cases may be quite large?

I am hoping someone can suggest a script/function in basic JS that can (1) set up each random subarray, then (2) create the final 6 item array.

Kind Regards,

Answer 1

If you’re restricted to a sub-set of the modern JS API, I would probably take the approach of first merging the two arrays (iteratively) then applying a random sort. Something like:

var arr1 = [1,2,3], arr2 = [4,5,6];
for (var i=0, len = arr2.length; i<len; i++) arr1[arr1.length] = arr2[i];
arr1.sort(function() { return 0.5 - Math.random(); });

arr1 is now an array of the 6 numbers in random order, no repeats.

[EDIT] – based on the discussion below, try this.

//prep - two arrays, randomised order
var arr1 = [1,2,3].sort(r_sort),
    arr2 = [4,5,6].sort(r_sort),
    final_arr = [],
    smallest_array = arr1.length < arr2.length ? arr1 : arr2;
function r_sort() { return 0.5 - Math.random(); }

//build final array - intersecting the two arrays
for (var i=0, len = smallest_array.length; i<len; i++) {
    final_arr[final_arr.length] = smallest_array[i];
    if (smallest_array == arr1 && arr2[i])
        final_arr[final_arr.length] = arr2[i];
    else if (smallest_array == arr2 && arr1[i])
        final_arr[final_arr.length] = arr1[i];

}

//result
alert(final_arr);